Boronic Acid-Catalyzed Selective Oxidation of 1,2-Diols to a-Hydroxy Ketones in Water

The activation of 1,2-diols through formation of boronate esters was found to enhance the selective oxidation of 1,2-diols to their corresponding -hydroxy ketones in aqueous medium. The oxidation step was accomplished using dibromoisocyanuric acid (DBI) as a terminal chemical oxidant or an electrochemical process. The electrochemical process was based on the use of platinum electrodes, methylboronic acid [MeB(OH)(2)] as a catalyst and bromide ion as a mediator. Electro-generated OH- ions (EGB) at the cathode acted as a base and Br+ ion generated at the anode acted as an oxidant. Various cyclic and acyclic 1,2-diols as substrates were selectively oxidized to the corresponding -hydroxy ketones via their boronate esters by the two oxidative methods in good to excellent yields.